Fixing a Leaking Stopcock: A Simple Guide

Fixing a leaking stopcock doesn’t always require calling in the professionals. 

You might be able to do it yourself if you can identify the right stopcock parts and use some basic tools.

Stopcock: A definition

A stopcock (sometimes called a stop tap) is the mains valve that controls the flow of water into your property. 

It is always switched “on”. But you can turn it off if you have a leak or are carrying out repairs, maintenance or home improvements.

A functioning stopcock is the quickest way to turn off the water supply to your home if you have a burst pipe or broken internal tap.

There are two stopcocks for your home: 

• One is located outside the property. This is the responsibility of your water supplier to fix if there is a leak. 
• The other is located inside your home. It’s usually under your kitchen sink or in a downstairs toilet. 

You should know where your stopcock is located so that you can quickly turn off the water supply during a leak. 

There are different models of stopcocks, but they will all have similar parts. 

Understanding these parts will help you identify problems quicker.

Compression nuts

If water is coming out of your stopcock, then the problem is either with the compression nuts or the gland nut (see below). There are two compression nuts on either side of the stopcock which join the tap to the water pipes on either side.

Fixing compression nuts

Step 1: The basic fix

Fixing compression nuts is easy and usually only requires water pump pliers and a spanner. If you can see water leaking from the compression nuts on either side of the stopcock, you may just need to tighten them. 

To do this, grip the body of the stopcock with the pliers and use your spanner to turn the compression nut in a clockwise direction.

Step 2: Creating a seal

If step 1 doesn’t stop the leak, you may need to create a seal with PTFE tape.

1. Switch off the water supply to the stopcock. Do this by turning off the external stopcock. This may be located in a drain outside your home.
2. Drain the water in the system. Turn on a tap and wait for the system to empty.
3. Loosen the compression nut. Grip the stopcock with the pliers and use the spanner to loosen the nut.
4. Wrap and replace. Wrap the thread with PTFE tape and then replace the nut.
5. Turn your external stopcock back on.

Gland nut

If water is coming out of your stopcock, and the issue isn’t the compression nuts, it could be the gland nut. The gland nut sits below the stopcock. It prevents water from flowing up inside the spindle.

Fixing gland nuts

Step 1: Turn off the external stopcock

Locate and turn off your external stopcock to avoid water leaking during the following steps.

Step 2: The basic fix 

 Fixing a gland nut is relatively easy and only requires a spanner. Like the compression nut, it can easily be tightened. 

Tighten the gland nut with a spanner. Be careful not to tighten this too much as it could prevent you from turning the stopcock.

Step 3: Replace the packing

If step 2 doesn’t fix the problem, you may need to replace the packing. This is a more difficult task that requires spanners, a screwdriver, and PTFE tape/packing.

1. Use one spanner to hold the large nut on the stopcock and the second spanner to loosen the gland nut
2. Slide the gland nut up the spindle using a screwdriver to manoeuvre it
3. Remove any old packing debris and then wrap the gland in PTFE tape or packing
4. Gently push this back into the gland and then tighten the gland nut
5. Turn your external stopcock back on.

Head gear joint

If water isn’t coming out but the stopcock doesn’t stop the flow of water when it’s in the “off” position, the problem is likely the head gear joint.

The head gear joint is the mechanism inside the stopcock which stops the flow of water. 

A leaking gear head joint is the result of a broken or eroded washer. The washer is located at the base of the spindle and it is the mechanism that stops the flow of water. 

Fixing this is difficult because there are more steps and a higher risk of pipework damage. It also requires more tools:

• Water pump pliers
• Screwdriver
• Spanner
• Replacement washer
• PTFE tape.

The fix: replacing a head gear joint 

To replace this, you will need to take the following steps:

1. Turn your external stopcock off to isolate the water to your home and drain the pipes.
2. Loosen the large nut in the centre of the stopcock. Use your spanner and water pump pliers
3. Remove the entire stopcock and spindle. Unscrew the tap to do this
4. Replace the old washer with a new one
5. Wrap PTFE tape around the bottom of the spindle. This is just above the washer. 
6. Replace the spindle
7. Retighten the nut.
8. Turn the external stopcock back on.

Home cover protection

If you want complete protection from leaks and breakdowns, YourRepair home cover can help you. 

We offer a range of plans covering everything from your boiler to your electrics and everything in between.

Get in touch today to find out more about home and boiler care plans.